public class Test8 {
    public static void main(String[] args) {
        StringBuilder stringBuilder = new StringBuilder();
        stringBuilder.append("1");
        stringBuilder.appendCodePoint(1);



        StringBuilder s1 = new StringBuilder("hello");
        String s2 = s1.toString();
        s1.append(s2);
        StringBuilder s3 = new StringBuilder(s2);

        s1.append("hello");

        StringBuilder str1 = s1;
        s1.append(" world");
        System.out.println(str1);


        String str2 = s2;
        s2+=" world";
        System.out.println(str2);
    }
}
